The water regulator for England and Wales is to investigate why thousands of homes suffered water shortages in the wake of the recent cold weather.
Homes and businesses faced days without running water after pipes burst during a thaw which followed freezing weather conditions.
Ofwat will look at how prepared water firms were and what support they subsequently offered customers.
It said at the time that companies had "fallen well short".
Some water companies handed out bottled water as some households were without a mains supply for three days.
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More than 20,000 homes were affected in London, where schools were forced to close and people were advised to take shorter showers as Thames Water repaired burst pipes.
Both suppliers and customers affected will contribute to the review.
"To be left without a vital public service like water – in some cases for several days – is deeply distressing, particularly for those in vulnerable circumstances, " Ms Fletcher said.
The review is due to publish its findings by June 15.